1. Field of the Invention
This invention relates generally to oils seals, and more particularly to oil seals for a seal between an outer stationary housing and a central rotating shaft.
2. Related Art
Shaft seals for establishing a fluid tight seal between a stationary housing and a rotating shaft are well known. Continual efforts are made to attain a fluid tight seal, while minimizing the effects of friction between the seal and the rotating shaft. Some shaft seals utilize garter springs to facilitate maintaining a seal lip of the seal in sealing engagement with the shaft. Although these types of seals can prove useful, they typically result in an increased overall cost due to manufacture processes involved and in material cost of the springs. In addition, they can result in increased space requirements to accommodate the spring, and in addition, typically increase the weight of the seal assembly.
In another known shaft seal configuration, a reverse seal lip configuration is provided, wherein the seal lip has a sealing surface for engagement with the shaft and a reverse folded hinge portion lies substantially parallel in overlapping relation to the seal lip in an assembled state. The seal relies largely on the reverse folded configuration of the hinge portion to maintain the sealing surface of the seal lip in sealing engagement with the shaft. Although this configuration can prove useful in establishing a tight seal with relatively minimal friction in use, it does have potential problems both during assembly and in use. During assembly, the hinge portion can unfold if too much friction occurs between the sealing surface of the seal lip and the shaft. If this occurs, the seal needs to be removed and a new seal put in its place. If the problem goes undetected, a seal will not be established between the shaft and the housing, and problems associated with leakage will quickly result. In addition, even if the seal is installed properly, the hinge portion can unfold in use, thereby resulting in leaking problems thereafter. One contributing factor to the hinge portion unfolding in use is an increase in pressure on the oil side relative to the air side of the seal. If the pressure becomes too great on the oil side, the hinge portion can be pushed toward the air side of the seal until it eventually unfolds. As such, this type of seal has potential set backs both in assembly and in use.